1. Field of the Invention
The present invention relates to sound transducers generally and, more particularly, but not by way of limitation, to a novel flexural plate sound transducer having a low resonant frequency.
2. Background Art
Flexural plate sound transducers are widely used for producing sound from electrical signals or electrical signals from sound and are used especially in sonobuoys as both projectors and receivers of sound waves. Typically, such a transducer includes a cylindrical aluminum housing having an aluminum flexural plate extending across the interior of the housing orthogonal to the major axis of the housing. Ceramic piezoelectric elements are attached to at least one of the upper and lower surfaces of the flexural plate. The plate may be formed of one piece with the housing or it may be attached thereto with epoxy, bolts, or other, similar attachment means.
The resonant frequency of a conventional flexural plate transducer is controlled by the diameter of the plate, the plate thickness, and the outer edge mounting condition. This frequency is proportional to (h.sup.3 /a.sup.4).sup.1/2, where "h" is the plate thickness and "a" is the plate radius. It is desirable that the resonant frequency be as low as possible while maintaining a given package size; however, in general, it is very difficult to repeatably control the edge mounting conditions of a flexural plate transducer using standard mounting techniques.
Particular features, elements, and advantages of the present invention, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.